Big Brains Do Not Need Carbs

Evolution. It is a complex and interesting process.1,2,3,4,5,6,7,8,9,10 Whether you agree with Jerry Coyne or not, there is much fascination with what exactly has led us to the current bodies and brains which we inhabit.11,12,13,14,15,16,17,18,19,20 Two weeks ago The Quarterly Review of Biology published a controversial paper entitled “The Importance of Dietary Carbohydrate in Human Evolution.”21 Its preceding press release22 added “Big Brains Needed Carbs,” ensuring the controversy-eager media would jump all over the publication, including the University of Sydney, home of the GI Foundation. Of course this media frenzy23,24,25 is without critical analysis, and is simply a regurgitation of the same story. So the researchers behind this paper argued that as humans evolved from our Paleolithic ancestry, we needed carbohydrates (particularly starch) in order to develop larger brains.

While certainly generating a large amount of buzz and receiving tremendous media attention, this scientific paper is severely flawed. Quite frankly, it is fairly baffling that it was able to survive the peer review process at all. There are a number of points that are incorrect, so without further ado, let’s delve into the details of exactly why we did not need starch, in order to help develop our current brains.

To start, researchers for the paper cite the use of fire as a key point in their argument. However, they incorrectly lead the reader into believing that the timeframe for humans using controlled fire was about 300,000-400,000 years ago, when they themselves contradict this with the statement that “the timing of widespread cooking is not known.” This is likely one misfire that should have been caught in the peer review process. In reality, our ancestors could only make fire in a controlled fashion, starting about 75,000 to 125,000 years ago.26,27,28,29,30,31,32,33,34 Hominid encephalization (enlargement of the brain), by contrast, began about 2 million years ago. 35,36,37

This is in addition to the researchers’ lack of scientific support for starch consumption compared with non-starchy vegetables, and the necessity of these foods in the human evolutionary process. And, if one were to veer to modern research, they would plainly see studies have proven a Paleo diet does not need to be high in starches or carbohydrates to vastly improve health.38,39 Further, it is widely accepted that hepatic de novo gluconeogenesis (a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates) can provide brain and placental tissue with all the glucose required even on a carbohydrate free diet. The fact that previously published research by the paper’s author supports this,40 is a glaring inconsistency that is hard to reconcile.

Suggesting early Homo acquired the capacity for endurance running as essential to exhaust prey is a weak assumption. This reference to persistence hunting, a method of hunting that utilizes the better thermoregulation of humans as compared to their prey, is only successful in a few select climates where thermoregulation is an issue. More importantly, the authors are clearly unaware of the research that measured the energetic cost of human running at different speeds.41 Researchers found, contrary to previous beliefs, individual humans do have optimal running speeds with respect to energetic cost, but it was also demonstrated “that the use of persistence hunting methods to gain access to prey at any running speed, even the optimum, would be extremely costly energetically, more so than a persistence hunt at optimal walking speed.” No starch is necessary for that. Even if the analysis on running efficiency were incorrect, and researchers proved persistence hunters did run at high intensities, the authors would need to explain the disconnect with their hypothesis with the fact that many present-day elite endurance athletes are succeeding on a low carbohydrate diet.

The fact is, our ancestors likely ate whatever they could – a fact, which is noted by modern Paleo diet researchers.42,43 Current science supports the notion that dense acellular carbohydrates in the diet promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity.44 This is why modern Paleo diet research is conducted with the design of eliminating foods not available during the pre-agricultural period – rather than focusing on specific amounts and quantities of foods.

These researchers also fail to cite a very recent paper, which examined nuclear genome sequence data from Neandertals, Denisovans, and archaic anatomically modern humans.45 It was concluded “salivary amylase gene (AMY1) duplications were not observed in the Neandertal and Denisovan genomes, suggesting a relatively recent origin for the AMY1 copy number gains that are observed in modern humans. Thus, if earlier hominins were consuming large quantities of starch-rich underground storage organs, as previously hypothesized, then they were likely doing so without the digestive benefits of increased salivary amylase production.”

As you can see, there are a myriad of flaws in this paper. The conclusions reached by the authors contradict everything we know about uncooked starch metabolism in our gastrointestinal tract, the archaeological evidence for fire production, and the brain’s requirement for docosahexaenoic acid (DHA).46,47 DHA was obtained by our ancestors, from animal foods – not starch – in order to synthesize nervous tissue.48,49

Lastly, perhaps one of the most interesting flaws in this paper is that many scientific studies concluded chronically elevated blood sugar (which is directly influenced by carbohydrate consumption) is correlated with dementia.50 Certainly this is the exact opposite conclusion than the one reached by the paper’s authors, who would have you believe that we needed carbohydrates in order for our brains to thrive and develop.

Hopefully, it is clear we certainly did not need starch to develop our current brains, and in fact, too many carbohydrates (including starches) impair brain processes.51,52,53 The problem with this conclusion is not scientific – it is economic. For you see, it is quite easy to continually churn out starch-heavy foods and make a profit – as these foods are very cheap to produce. And, without an endorsement of carbohydrates, how could a company justify selling sugar water to us, en masse?54 Thanks to a diet rich in animal products and fat, you have a big enough brain to recognize the real scientific evidence and that unethical influences are at play here. Definitely some real food for thought.

Casey Thaler, B.A., NASM-CPT, FNS

Casey Thaler, B.A., NASM-CPT, FNS is an NASM® certified personal trainer and NASM® certified fitness nutrition specialist. He writes for Paleo Magazine® and for PaleoHacks. He also runs his own nutrition and fitness consulting company, Eat Clean, Train Clean®. He is pursuing his Ph.D in Nutritional Biochemistry, hopefully from Harvard University.

Dr. Mark J. Smith

Dr. Mark J. Smith graduated from Loughborough University of Technology, England, with a Bachelor of Science in PE & Sports Science and then obtained his teaching certificate in PE & Mathematics. As a top-level rugby player, he then moved to the United States and played for the Boston Rugby Club while searching the American college system for an opportunity to commence his Master’s degree. That search led him to Colorado State University where Dr. Smith completed his Masters degree in Exercise and Sport Science, with a specialization in Exercise Physiology. He continued his studies in the Department of Physiology, where he obtained his Doctorate. His research focused on the prevention of atherosclerosis (the build up of plaque in arteries that leads to cardiovascular disease); in particular, using low-dose aspirin and antioxidant supplementation.

Dr. Loren Cordain is Professor Emeritus of the Department of Health and Exercise Science at Colorado State University in Fort Collins, Colorado. His research emphasis over the past 20 years has focused upon the evolutionary and anthropological basis for diet, health and well being in modern humans. Dr. Cordain’s scientific publications have examined the nutritional characteristics of worldwide hunter-gatherer diets as well as the nutrient composition of wild plant and animal foods consumed by foraging humans. He is the world’s leading expert on Paleolithic diets and has lectured extensively on the Paleolithic nutrition worldwide. Dr. Cordain is the author of six popular bestselling books including The Real Paleo Diet Cookbook, The Paleo Diet, The Paleo Answer, and The Paleo Diet Cookbook, summarizing his research findings.

The Paleo Diet, the world’s healthiest diet, is based upon the fundamental concept that the optimal diet is the one to which we are genetically adapted. The therapeutic effect of The Paleo Diet is supported by both randomized controlled human trials and real-life success stories.

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” In reality, our ancestors could only make fire in a controlled fashion, starting about 75,000 to 125,000 years ago…”
Dr. Curtis Marean would take issue with this as he and his team have found charred shellfish remains dating back164,000 years.
Collecting shellfish and other seafood, aquatic plants and animals would require relatively little energy expenditure, while providing tremendous quantities of DHA to fuel rapid brain growth and evolution. Here’s a short interesting video on the topic by Dr. Leigh Broadhurst from the University of Maryland: http://youtu.be/1S8Hb-4EAjI

I emailed Hardy my rebuttal and she never responded. The journal, QRB, disagreed about publishing my rebuttal for the following (incredible) reasons:

“I don’t think point number one is very strong. I brought this point up with the authors of this article and they agreed that humans can function normally without carbohydrates in their diet. Kidneys fail with a diet of above 45% animal protein. So a diet without carbohydrates has to be high in fat. As strict vegetarians show, animal protein is not required for optimal brain function. The question raised by Hardy et al was the presence of cooked carbohydrate gave enough extra energy in the form of glucose that it released a break on increase in brain size. The importance of this depends upon when in human evolution the return to camp and sharing of food evolved. I have always assumed that this happened during the evolution of Homo erectis. The selective agent could be social interaction or any of the other possible agent.

Point 2 is also weak in that the extra carbohydrate from starchy tubers could decrease the requirement for low energy plant foods. Carrying tubers to a camp site would be easier than the kind of plant material chimps and especially gorillas eat. If this is the case, then one would expect the ratio of plant and animal material to remain the same.

Point 3. I am familiar with this kind of dating being a molecular evolutionist. I have not read this particular paper. Did they take account of the possible homogenization of copies due to random increases and decreases in copy number and the possibility that this is a biased process that has very uneven probabilities of the elimination of certain copies and not others. These processes can easily cause a very large underestimation of the date of the initial increases. Unless the paper is extremely careful, I would not place much weight on the 200 kya.

Point 4. I am under the impression that the taming of fire happened some 800,000 years ago. Once agin I have not read the paper and do not understand how one site can contradict the evidence usually cited from Africa.

So my general answer to a commentary is no. However, your points suggested on possibility. That is to do a commentary on the time line assumed in the paper about the importance of dietary carbohydrate in human evolution.

I was appalled when I read an article, based an allegedly peer-reviewed study, claiming that paleolithic man ate largely straches – and that it was because of this that they had more rapid brain growth (if that is even an established fact).

I know from much study that human brain size has decreased, and continues to do so, sinze the advent of civilization and agriculture. In fact if one is so inclined, one can look at the data and create a linear trend showing the correlation between increased consumption of carbohydrates (i.e. agricultural products, which man began to consume around approx. 8500BC) and the generational decline in brain size. But I am no scientist, I’ll let someone else put that data together. There are countless other variables that could be the cause for the decrease in brain size, that also came about at the same time as agriculture – unsurprisingly.

But the simply logic that human could gather enough tubers to make them a large part of theri diet is simply absurd. I would love for a botanist to weigh in and tell where on earth you could find enough wild tubers to use as the mainstay of your diet. If this were possible Inuit, Eskimo, and First Nations people would have been consuming these in climates similar to that which early man resided in. In fact if they were a viable food soruce, tribal “native” Americans would have been consuming these concomitantly at the arrival of Europeans to teh New World… As this clearly is not the case, as corn and squash production, not tuber gathering, was necessitated among tribes preferring agricultural over hunting.

Anyways, you break down Hardy et al. misinterpreted, misquoted, and misunderstood the studies they cited – and how recent data has contradicted claims made by them both in genetics and isotope analysis.

This just leads to more confusion for me. If everything written here is true and the paleo-diet is key to being healthy, why do all the blue-zone diets, such as Okinawa, Sardinia, and Ikaria, where people live the longest and have the least instances of heart disease, diabetes, and cancer all have the same common trait? All of there diets contain almost no meat, or animal products, and most of their diet consists of hearty grains, vegetables, and fruits. Even on the island of Okinawa, fish is consumed only 2-3 times a week in portions of just a few ounces and any other meat, usually pork, is consumed about once per month, and the rest of the diet is root vegetables, seaweed and other assorted veggies and beans. These areas also have the least instances of dementia and brain function decrease of the global population. If what you are saying is true, logic should show that these people should live short, unhealthy lives, and have all manner of cognitive problems later in life. And before you play the “genetics” card, studies have shown that these populations have almost no significant genetic variation from their more unhealthy countrymen and women. In fact, as these areas have been opened up more to the outside world and their consumption of meat increased, so did instances of obesity, cancer, heart problems, cholesterol increase, etc..

Thank you for your question about comparing the Paleo diet and the Blue-zone diets. The first point I’d make is that there are obviously a multitude of factors that contribute to longevity. Dr. Cordain referred to this in an article he wrote discussing The Cannonau grape from Sardinia and its contribution to longevity when he stated “Environmental factors including diet, exercise, fresh air, sunshine, occupation, psychological factors including positive outlook, meaningful life roles, close family ties, spiritual perspective and hereditary factors all work synergistically to promote a long, healthy lifespan. It would be difficult or impossible to quantify the precise role each of these elements may play in maximizing human longevity.” Dan Buettner’s book The Blue Zones obviously goes into great detail about these many factors that contribute to the unusually high percentage of centenarians in the blue zones and I think the vast majority of individuals that have found success in adopting a Paleolithic dietary template, would agree that the lifestyle choices that individuals living in blue zones have made would be good choices to make themselves and many, in fact, do include many other beneficial lifestyle choices outside of just the diet. The Paleo diet template itself is supported by thousands of peer-reviewed scientific papers and in recent years a growing number of experimental studies are showing the physiological benefits of adopting the Paleo diet. With the growing popularity of the Paleo diet (which would NOT have happened if it was not successful in improving people’s wellbeing), an ever- increasing number of individuals have attempted to “debunk” the Paleo diet and we have written many responses to these flawed arguments here at ThePaleoDiet.com. A simple question we often ask is, demonstrate how one can improve upon a Paleolithic diet by conducting a nutritional analysis on a week’s worth of Paleo meals and a week’s worth of whatever diet it is that is being argued as a better alternative for human consumption. I could ask the same of anyone wanting to compare a typical blue-zone diet to the Paleo diet. And while you mention that opening up these areas to the “outside world” has increased chronic disease, this does not denounce a Paleo diet in any way since obviously the “outside world” is not following a Paleo diet; at least not yet. While some studies have shown a correlation between an increase in meat consumption and chronic disease, these studies have not separated out the effects of consuming processed meat or grain-fed meat from natural meats such as grass-fed beef. The Paleo diet template does not include the consumption of processed and grain-fed meats and advocates concur that an increase in their consumption could contribute to increased morbidity. No study has shown that naturally occurring animal protein consumption, even in high quantities, has resulted in an increase in the incidence of chronic disease. Another question that could be asked is, if the diets of the blue zone locations were replaced with a Paleo diet, would we see a reduction or an increase in the percentage of centenarians? I’m very confident that we would not see a reduction and the science would support a potential increase. However, that is speculation until that research is actually conducted. Such research could also prove to be helpful in attempting to quantify the role of each of the elements identified in increasing longevity. In the mean time Jeremy, my guess is that a better view of the answer will arise as the Paleo diet popularity continues and maybe we’ll even get to compare it to the outcome of Dan Buettner’s mission to spread the blue zone lifestyle across North America. Which ever camp someone decides to reside in, I’m also confident that they will be far better off than continuing a lifestyle and diet typically seen in today’s western world.

Thank you so much for providing such strong and well supported evidence proving starch as a carbohydrate was not a factor in hominid evolution, much less brain development. Even though the hunter-gathers were scavengers and would eat anything they could, especially in times of scarcity. Most likely would have been impossible for hominids to have been capable of safely ingesting cereal grains (such as wheat, corn, beans, soy, and potatoes/tubers and rice) even in their per-Neolithic forms WITHOUT first cooking. These prevalent modern food sources can be described as nothing short of sugar bombs that have additional harmful compounds and side affects. As fire and cooking have probably been around for less than .15 MYA, the diets of those from .15 to 4 million years ago were probably relatively balanced with protein, fats and healthy complex carbohydrates from whole fruits, berries and vegetables, along with honey if they could find it and get it without being harmed too much by the producers of the honey. Those precious little bees give us the best pure energy source loaded with literally thousands of micro- nutrients found on Earth. However, honey is approximately 50% sucrose so will increase blood sugar levels quickly (glycemic index), so honey must be consumed in moderation relative to the level of exertion. (Calories in = calories out)

Honey wasn’t particularly difficult to find with the help of the Greater Honeyguide. It’s a wild bird that evolved to talk to humans and guide them to hives of honey.

In fact, the co-evolution of humans and the honey guide is so strong that Richard Wrangam called this remarkable interaction “the most developed, co-evolved, mutually-helpful relationship between any mammal and any bird.”

This co-evolution is believed to have developed between 3 to 5 million years ago. The behavior is so ingrained in the honeyguide that they continue to bring the Masai and Hadza to hives of honey despite the fact that the Masai do not reward them.

Thanks to the evolution of the honeyguide, it should be obvious that humans were heavily reliant on honey.

Finally, the Masai and Hadza also have access to honey from stingless bees. Studies have shown that even lesser primates have been known to build tools to extract honey from hives.

There is no culture on earth that, before agricultural production honey, found enough of it to make it a frequent component of their diet – much less the mainstay of it.

Honey in every culture has always been a treat until modern times. Otherwise we would of been sweetening all of awful foods with it before sugar production.

And the trope about Greater Honeguides is just that – a trope you will see in media and poorly researched articles. The behavior surely exists, but what you hear and read about it is an exaggeration of reality that makes for a great story. I encourage to read about the Greater Honeyguide:

Sure every one in a while a honey-badger can be attracted to honey by a bird, I don’t doubt that – though again videos purporting to show it are sketchy, and it is not documented as an actual behavior. They may learn that people can get them honey, that has been said to been found. But a reliance on this as theory for people having a regular supply of honey is absurd. Honey is rare for man before the advent of larger civilizations and agriculture. If the honeyguide leading to honey event was common, or easy, honey consuming animals would have been exploiting the behavior all the time – bears, humans, monkeys, every dang omnivore. It would be a common symbiosis if it proved practical, evolution would necessitate that.
And honey is just is not that easy to find, and even if you had an army of Honeyguides, you wouldn’t have enough to make it anything other than a treat.

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